1. Statement of the Invention
This invention comes within the scope of asynchronous time-division switching. More specifically, the invention relates to communication systems associated with asynchronous time-division networks authorizing no-connection mode communications between terminals.
2. Brief Description of the Prior Art
Asynchronous time-division networks are designed to supply with-connection mode communications, i.e. a link with allocation of resources must necessarily be set up between terminals prior to each transmission of data. Local Area Networks (LAN) provide services of the no-connection type and a terminal can at all times transmit data to another terminal by simply specifying the address of the destination terminal without any need for prior setting-up of a link. A no-connection service is essential for data transmission applications for which the following are not known a priori:
With which other terminals will the calling terminal subsequently exchange information? PA0 What volume of information will said calling terminal transmit, for how long and at what rate? and PA0 At what moments will the calling terminal be transmitting?
In fact, such unpredictability at the parameter level of a communication makes the profitability of with-connection service relatively low. The load factor of a link is unknown and, in the event of a transmission request, the setting-up time of the link risks being disproportionate to the period of transmission of information.
The asynchronous time-division technique is generally considered to be a very good technical solution for switching on account of its speed, and its utilization is considered for the constitution of future wideband integrated services digital networks (WB-ISDN). Given the qualities and assets of this technique, it is desirable that it be able to meet the different communication needs. An asynchronous time-division network must be able to meet the demands of no-connection services if only for it to be also utilizable in the private field of Local Area Networks.